The invention relates to a device for interrupting the feed of a roving to the drawing frames of a spinning machine, wherein each drawing frame comprises a plurality of upper and lower drawing rollers arranged pairwise, of which a lower drawing roller is provided with a clamping segment, at its roving feed side, which is held against movement with the lower drawing roller by a locking device that is triggerable by means of a broken-end detector which monitors the moving thread. The locking device, which automatically drops into its locking position, is provided with an electric drive, said drive being controllable by the broken-end detector and being energizable for a preset time interval, said drive acting to displace the locking device into an unlocking position. Such an arrangement is described in commonly assigned, pending U.S. application Ser. No. 331,281, filed Dec. 16, 1981; now U.S. Pat. No. 4,432,195.
In such an arrangement, the clamping segment, during normal operation, is held by the locking device in a position which permits unimpeded feeding of the roving between the drawing rollers. In the event of a thread break, a broken-end detector effects a temporary energization of an electric drive mounted on the locking device, so that the clamping segment is unlocked and rotated up to a stop disposed between the two drawing rollers on the roving-feed side, whereby it clamps the roving against the upper, non-driven drawing roller and lifts the latter simultaneously away from the lower, driven drawing roller. Since the electric drive is energized for only a preset interval, after this time has elapsed, the locking device automatically is permitted to resume its original position, i.e., the locked position. In order to initiate roving feed, the clamping segment need only be turned back into its original position, in which it is engaged by the locking device. No further intervention by the operator is required. The device ensures reliable and rapid interruption of roving feed after a thread break and, as a rule, prevents the formation of fiber laps on the drawing rollers (i.e., fibers improperly wound around the drawing rollers). The goal of the present invention is to avoid formation of fiber laps even more reliably. This goal is achieved, in accordance with preferred embodiments of the present invention, by virtue of the fact that suction devices are associated with the drawing rollers on the thread-forming side.
Since the forward pairs of drawing rollers of the arrangement of above noted Ser. No. 331,281 continue rotating independently of the energization of the device for interrupting roving feed, the fibers which are still in this area, after fiber feed is interrupted, are carried further without, however, being spun into a thread. The device, according to the present invention has, therefore, been designed so as to ensure that these fibers, located between the clamping point of the roving and the thread-break location, will likewise not be transported away in an uncontrolled fashion, but will instead enter the suction device. The danger of lap formation on the drawing rollers is further reduced by this measure. The present invention also has the advantage that the fibers which enter the suction device are not wasted and can be reused.
In order to facilitate the removal of fiber laps which do manage to form on the drawing rollers, in another aspect of the preferred embodiment of the invention, accessibility to the drawing rollers, despite the provision of the suction device, is ensured, since the suction devices can be moved away from the drawing rollers and are, preferably, lockable in their operating positions and nonoperating positions. Consequently, the position of the suction device can be modified rapidly and reliably to suite the conditions of the moment, since additional unlocking and locking of the suction device is eliminated.
In an especially simple embodiment, each suction device is designed as a suction tube, mounted, by its end away from the drawing rollers, pivotably on the drawing frame or machine frame, and having a connection for a hose connected or connectable to a vacuum source.
In accordance with another feature of the preferred embodiment of the invention, provision is made for the suction tube, made of an elastically flexible material, to be guided as it swivels away in a guide eye within a guide slot, the eye being arranged on the drawing frame or machine frame, the width of said slot at the locking positions corresponding to the outside diameter of the suction tube, and being narrower in the other areas relative to the outside diameter of the suction tube. This results in an especially sturdy and economical device for locking the suction device.
In accordance with yet another advantageous feature of the disclosed embodiment, the broken-end detector is provided with a feeler resting against the moving thread, said feeler being in the form of a pivotably mounted flat plate. A thread feeler of this kind is very light, since it is made, for example, of coated plastic. It can have a strikingly bright color, and thus serve as a signal, which can be seen from a distance, indicating that a thread break must be corrected.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, a single embodiment in accordance with the present invention.